Iris: care, varieties & propagation
Irises are hardy perennials that add a pop of colour to your garden year after year. Find out everything about their flowering period and different iris varieties as well as how to care for and propagate irises in our guide below.
As a magnificent perennial of early summer, the iris has long been a popular garden plant. There are countless iris species and cultivars whose flowers bloom in many different shades and colour combinations. Irises really do come in all the colours of the rainbow, as their name suggests. “Iris” comes from the Greek word for a “rainbow”, which is also the name for the Greek goddess of the rainbow.
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Iris: flowering time, origin and characteristics
Irises (Iris) are a genus of plants in the iris family (Iridaceae) and have been in our gardens for centuries. The many species of iris are widespread in the temperate zone of the northern hemisphere. Probably the best known and most intensively cultivated iris species is the bearded iris (Iris barbata). Bearded irises are divided into three groups according to height and flowering time. The shorter an iris type grows, the earlier it flowers. The tall bearded iris (Iris barbata elatior) group is made up of large irises that grow to a height of 60 to 120cm and flower from late May to mid-June. These are the largest of the bearded irises, while also being the last to bloom with the largest flowers. Somewhat earlier in May, intermediate bearded irises (Iris barbata intermedia) flower, their stems growing 40 to 60cm tall. The dwarf bearded irises (Iris barbata nana), which grow to a maximum height of 40cm, flower as early as mid-April, making them one of the first heralds of spring. They are ideal for rock gardens and borders.
Less well known, but just as elegant, is the blue iris (Iris spuria). Growing up to 150cm high, the blue iris looks spectacular in the garden grown beside the somewhat smaller Siberian flag (Iris sibirica). With a flowering time of February to March, the dwarf iris species Iris reticulata and Iris danfordiae are among the earliest blooming iris species. The Japanese water iris (Iris ensata) looks beautiful on the edges of ponds in various colours from pink to blue to violet and grows 80 to 100 centimetres high.
Iris flowers are made up of 3 inner and 3 outer petals. The bearded iris’ inner petals, called “standards”, are turned upwards and closed. They form a sort of dome, which is much less noticeable in other iris species. The 3 outer leaves, called “falls”, hang down at the sides. The upper part of the outer petals also has a bushy, brush-like structure which gives the bearded iris its name.
All the iris species mentioned have narrow, sword-shaped and upright leaves. They are usually deep green to grey-green and sometimes have a slightly bluish tinge. Depending on the species, they grow from iris tubers (Iris tuberosa), iris rhizomes (rhizomatous irises) or iris bulbs (bulbous irises).
Iris varieties: the most beautiful irises for the garden
The above species come in a wide range of varieties. These are our top picks for the most beautiful irises to grow at home:
Tall Bearded Iris (Iris Barbata Elatior group)
- ′Kupferhammer′: Robust and flowering variety from 1930; yellow standards, mahogany-red falls, marbled in the middle, orange beard; height: 40cm; flowering time: May-June.
- ′Provençal′: Burgundy falls with yellow centre; height: 85cm; flowering time: May-June.
- ′Proud Tradition′: Silver-blue standards, wide ruffled deep violet-blue falls; height: 100cm; flowering time: May.
Intermediate Bearded Iris (Iris Barbata Intermedia or Iris Barbata Media group)
- ′Arctic Fancy′: White waved standards with broad violet margins, white falls with a narrow violet edge; height: 50cm; flowering time: May-June.
- ′Swizzle′: Golden yellow flowers; height: 50-70cm; flowering time: May-June.
- ′Con Brio′: Red purple falls, violet standards; fragrant flowers; height: 60cm; flowering time: May and September.
Dwarf Bearded Iris (Iris Barbata Nana group)
- ′Little Buccaneer′: Maroon flowers, yellow beard; height: 25cm; flowering time: April-May.
- ′Church Stoke′: Violet standards, red purple falls (red deepening in the centre), yellow-white beard; fragrant; height: 25cm; flowering time: April-May.
- ′Soft Air′: Cream-white flowers, yellow-white beard; height: 30cm; flowering time: April-May.
Blue Iris (Iris spuria)
- ′Betty Cooper′: Yellow flowers with fine lavender lines and delicate purple edges; height: 120cm; flowering time: May – June.
- ′Archie Owen′: Radiant golden yellow flowers; height: 90-100cm; flowering time: June.
Siberian Flag (Iris sibirica)
- ′Butter and Sugar′: White sugar standards with a yellow sheen, butter yellow falls; height: 40-60cm; flowering time: May-June.
- ′Caesars Brother′: Small intense violet-blue flowers, striped yellow and white throat; height: 60-100cm; flowering time: May-June.
Dwarf Iris
- Iris reticulata ′Harmony′: Dwarf, bulbous iris with delicate cornflower-blue petals, marbled yellow-white towards the centre; height: 10-15 cm; flowering time: February-March.
- Iris histrioides ′Katharine Hodgkin′: Petals with light blue veins on a creamy-yellow base, deep yellow centre with dark blue spots; height: 15-25cm; flowering time: January-February.
Japanese Water Iris (Iris ensata)
- ‘Galathea’: Rather short and delicate standards, very broad falls often showing pretty veining; white-purple flowers; height: 80cm; flowering time: June-July.
Iris care: how to care for irises before and after flowering
Find out how to plant irises correctly and what location is best for each species in our article on planting irises. Below are some tips on pruning and fertilising irises. Tall varieties in particular should also be supported during the flowering period.
Pruning irises
Deadheading iris flowers after the flowering period prevents energy-intensive seed formation as well as fungal infections and diseases. Cut back the faded irises to about 10 centimetres. The foliage can be left standing; they are decorative elements in the perennial bed even in winter. If plants develop a fungal infection, cut back the leafy crown and the iris plants will sprout new foliage in midsummer. Some types of irises such as the tall bearded iris ′Total Recall′ or ′English Cottage′ respond to vigorous pruning after the first flowering with a second flowering phase in autumn.
Fertilising irises
Modern iris varieties need more nutrients than older varieties. Fertilise your irises at least once a year. The right time to do this is in March, when the perennials are starting to regrow. A second fertilisation can be applied in May. It is best to choose a slow-release, potassium-rich fertiliser, such as our Plantura Flower Food. This covers the iris’ nutrient requirements for the long term and supports their development into healthy and hardy plants.
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Watering irises
Water young iris flowers from time to time. Older iris plants that are well established in their location usually do not need to be watered. However, in the event of prolonged drought, water them just to be on the safe side.
Overwintering irises
Most iris species are hardy and can survive the winter months in the garden without additional protection. However, some species, such as the Siberian flag, are more sensitive to cold and need to be prepared for winter. Cut back the iris flower stems about 10 centimetres above the root ball and remove discoloured leaves and withered leaf tips. In autumn, cover the irises with a layer of leaves, mulch or straw so that they are not exposed to frost.
Propagating irises
One way to propagate irises is to divide the iris rhizomes in spring or after flowering. Even if you do not necessarily want to propagate the irises in your garden, we recommend doing this anyway. The iris plant’s flowering intensity often decreases after 3 to 5 years. But by dividing the iris rhizomes, the perennials are naturally stimulated to produce new iris flowers.
Dividing irises: step-by-step instructions
- Time: Late summer.
- Carefully dig the iris rhizomes out of the soil.
- Cut the rhizomes with a sharp knife into pieces with at least one fan of leaves on each rhizome (cut surface should be as small as possible).
- Shorten the leaves by about half (this will reduce evaporation and avoid weakening the plants).
- Select young, healthy rhizomes (the edge pieces are the strongest) and replant the fist-sized root balls.
- Water well.
As an alternative to root division, which produces pure irises (exactly the same as the parent plant), you can propagate irises from seed. Wait until the seed pods are ripe and then harvest the seeds. Irises are cold and dark germinators. Therefore, place the seeds in the refrigerator a few days before sowing. Sow iris seeds in a seed tray filled with substrate, cover seeds with a 2cm layer of soil and place in a sheltered spot. Our peat-free Plantura Organic Herb & Seedling Compost is ideal as a substrate. Keep moist at a temperature of about 15°C, so that the iris seeds can germinate and develop into new plants.
- Perfect for herbs as well as sowing, propagating & transplanting
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Are irises poisonous?
All parts of the iris plant, but especially the iris rhizomes, contain poisonous substances that cause serious symptoms of poisoning if eaten. Some of them can also cause skin irritation or even dermatitis when touched. Therefore, for safety’s sake, plant irises in a place inaccessible to children and pets and wear gloves when handling them.
Read our article on planting irises for more helpful tips on planting irises in your garden.
Want more inspiration for hardy perennial plants to grow at home? Read our article on hardy perennials.
